Home > Web Front-end > JS Tutorial > body text

Detailed introduction to the new features of JavaScript6

黄舟
Release: 2017-03-16 14:36:41
Original
1680 people have browsed it

JavaScript What’s new in 6? Let’s take a look at some of the new features of JavaScript 6.

  • let, const (used to define block-local variables), during the program process function

  • Destructuring: let {x, y} = pt; let [s, v, o] = triple();
    ( The premise is let pt = {x:2, y:-5})

  • Default parameter value: function f(x, y=1 , z=0) {⋯}

  • ##Other parameters: function g(i, j, ...r) { return<a href="http://www.php.cn/wiki/135.html" target="_blank"> r.slice(i, j); }</a>(No need to use
    arguments).

  • Data expansion:

    let a = [0,1,2,3], o = new<a href="http://www.php.cn/wiki/165.html" target="_blank"> Something(...a);</a>. Can also be used for array literals: [1, ...array<a href="http://www.php.cn/wiki/1041.html" target="_blank">, 4]</a>.

  • ObjectAbbreviation:
    let one = 1; { one, func_one() {return 1;}, ['key<a href="http://www.php.cn/wiki/1051.html" target="_blank"> ' + one]: 1 }</a> .

  • FunctionAbbreviation (a) => a * a The effect is equivalent to
    (function(a) { return a * a; }).bind(this)

  • map, set: let m = new Map (); m.set(key, value); m.has(key); m.get(key). also includes
    .clear<a href="http://www.php.cn/wiki/917.html" target="_blank">()</a> , .delete<a href="http://www.php.cn/wiki/1298.html" target="_blank">()</a>, .forEach<a href="http://www.php.cn/wiki/127.html" target="_blank">()</a>, .keys().

  • Weak map:

    let map = new WeakMap(). Use it when there is a loop referencing . In the same waynew WeakSet().

  • promise:

    new Promise((resolve, reject) => {…}).

    • When

      promise.then(value => {…}), resolve(valueOrPromise) returns the promised value (or a new promise, forming a chain call)

    • When

      promise.then(…).then(…).catch(error => {…})reject(new Error(… ))Interrupt promise

    • Quick promise creation:

      Promise.resolve(value), Promise.reject(error).

    • Iteration:

      Promise.all<a href="http://www.php.cn/wiki/1483.html" target="_blank">(listOfPromises).then(listOfValues ​​=> …)</a>,
      Promise.race (listOfPromises).then(valueThatResolvedFirst => …)

    ##Proxy:
  • let obj = new Proxy(proto, han

    dler)<a href="http://www.php.cn/wiki/596.html" target="_blank">.</a>Simply put: Use elements of class objects for overloading
    (can bring all accessible attributes.)

  • Generator

    : function* gen() { yield 1; yield 2; }In fact, gen()
    will Returns an object containing the next()<a href="http://www.php.cn/wiki/1071.html" target="_blank"> function. </a>

  • Loop:
  • for (var [key, val] of items(x)) { alert(key + ',' + val); }

    .

  • Class definitions use
  • extends<a href="http://www.php.cn/wiki/166.html" target="_blank">, </a>super<a href="http://www.php.cn/code/8202.html" target="_blank">, and </a>static<a href="http://www.php.cn/wiki/188.html" target="_blank">:</a><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">class Point extends Base { constructor(x,y) { super(); this[px] = x, this[py] = y; this.r = function() { return Math.sqrt(x*x + y*y); } } get x() { return this[px]; } get y() { return this[py]; } proto_r() { return Math.sqrt(this[px] * this[px] + this[py] * this[py]); } equals(p) { return this[px] === p[px] &amp;&amp; this[py] === p[py]; } }</pre><div class="contentsignin">Copy after login</div></div>

  • Symbol object, creates a private key, which can be used in maps and classes (private members
  • members).

    let a = Map();
    {
      let k = Symbol();
      a.set(k, &#39;value&#39;);
      // 这里你可以访问和设置&#39;value&#39;,比如a.get(k)。
    }
    //这里不行,k是不可见的。
    Copy after login

  • Modular

    :

  • Template style
  • String

    : Can be multiple lines, And can embed variables. `You are ${age} years old.`
    .<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">// 多行字符串 re`line1: (words )* line2: \w+` // It desugars to: re({raw:&amp;#39;line1: (words )*\nline2: \w+&amp;#39;, cooked:&amp;#39;line1: (words )*\nline2: \w+&amp;#39;})</pre><div class="contentsignin">Copy after login</div></div>

  • Typed array

The above is the detailed content of Detailed introduction to the new features of JavaScript6. For more information, please follow other related articles on the PHP Chinese website!

Related labels:
source:php.cn
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template
About us Disclaimer Sitemap
php.cn:Public welfare online PHP training,Help PHP learners grow quickly!